Single-crystal material based on aluminium garnets

ABSTRACT

A single-crystalline material based on aluminium garnets of the general formula Re 3  Al 5  O 12 , wherein Re=Y, Dy, Ho, Er, Lu and containing a dyeing additive of a red color spectrum, viz. specifically zirconium, in an amount ranging from 10 -2  to 3% by weight.

FIELD OF THE INVENTION

The present invention relates to the art of artificial single crystals and, more specifically, to a single-crystal material based on aluminium garnets.

BACKGROUND OF THE INVENTION

Known in the art is a single-crystal material based on yttrium-aluminium garnet (Y₃ Al₅ O₁₂) containing chromium as a dyeing additive in an amount of 0.01 to 3% by weight. This material has a green colour and a red luminescence (cf. CSSR Pat. No. 152,908 Cl. B 01 J 17/02, published 08.12.71).

Also known is a single-crystalline Jewelry material based on yttrium-aluminium garnet, wherein as the dyeing additive titanium is used in an amount of from 1.10⁻⁴ to 1% by weight. This material has a clearly pronounced brown colour under daylight passing to a reddish colour at an artificial illumination (cf. USSR Inventor's Certificate No. 594628, Cl. B 01 J 17/00, Bulletin No. 17 published in 1978).

The use of these dyeing additives in the above-mentioned single-crystalline materials does not make it possible to obtain a red dyeing spectrum.

SUMMARY OF THE INVENTION

The present invention is directed to the provision of a single-crystalline material based on aluminium garnets which, through the selection of a novel dyeing additive, would have colours of a red spectrum.

This object is accomplished by that of a single-crystalline material based on aluminium garnets of the general formula: Re₃ Al₅ O₁₂, wherein Re=Y, Dy, Ho, Er, Lu and incorporating a dyeing additive containing, as the latter, zirconium in an amount of from 10⁻² to 3% by weight.

To impart a red colour to a single-crystalline material based on yttrium-aluminium garnet, it preferably contains zirconium in an amount of from 10⁻² to 3% by weight.

A single-crystalline material based on dyeprosium-aluminium garnet, for the purpose of imparting a red colour thereto, preferably contains zirconium in an amount of from 10⁻² to 3% by weight.

To impart a reddish-brown colour, a single-crystalline material based on holmium-aluminium garnet preferably contains zirconium in an amount of from 10⁻² to 3% by weight. A single-crystalline material based on erbium-aluminium garnet preferably contains, for the purpose of imparting a red-yellow-brown colour thereto, zirconium in an amount of from 10⁻² to 3% by weight.

To impart a red colour, a single-crystalline material based on lutecium-aluminium garnet preferably contains zirconium in an amount of from 10⁻² to 3% by weight.

The single-crystalline material according to the present invention, owing to the use of a novel dyeing additive, has a red colour spectrum sufficiently close to that of corresponding naturally-occurring almandine, pyrope, hessonites or hyacinth.

DETAILED DESCRIPTION OF THE INVENTION

The single-crystalline material based on aluminium garnets according to the present invention can be produced by known methods of growing refractory single crystals from a melt, e.g. using Bridgeman-Stockbarger, Chokhralsky methods, debiteuse and the like. Basically use is made of aluminium garnets of the general formula Re₃ Al₅ O₁₂, wherein Re=Y, Dy, Ho, Er, Lu. The dyeing additive is introduced into the starting material as zirconia (ZrO₂). For a better understanding of the present invention the following Examples illustrating the single-crystalline material according to the invention are given below.

EXAMPLE 1

A single-crystalline material based on yttrium-aluminium garnet Y₃ Al₅ O₁₂ containing zirconium as a dyeing additive in the amount of 0.01% by weight is prepared by the Bridgeman-Stockbarger method. A mixture of oxides consisting of the following components, percent by weight:

    ______________________________________                                                 Y.sub.2 O.sub.3                                                                      57.060                                                                   Al.sub.2 O.sub.3                                                                     42.926                                                                   ZrO.sub.2                                                                             0.014                                                           ______________________________________                                    

is charged into a molybdenum container, heated to a temperature of the order of 2,000° C. and crystallized at the speed of movement of the drawing mechanism of 2 mm/hr. The thus-produced crystal has a light-red colour.

EXAMPLE 2

A single-crystalline material based on Y₃ Al₅ O₁₂ containing zirconium as the dyeing additive in the amount of 0.75% by weight is produced in a manner similar to that described in the foregoing Example 1. As the starting components a mixture is used consisting of the following oxides, percent by weight:

    ______________________________________                                                 Y.sub.2 O.sub.3                                                                      56.06                                                                    Al.sub.2 O.sub.3                                                                     42.90                                                                    ZrO.sub.2                                                                             1.04                                                            ______________________________________                                    

The resulting crystal has a dark-red colour resembling that of almandine and pyrope.

EXAMPLE 3

A single-crystalline material based on dysprosium-aluminium garnet Dy₃ Al₅ O₁₂ containing zirconium as the dyeing additive in the amount of 1% by weight is obtained as described in a manner similar to that described in Example 1. As the starting components use is made of a mixture of oxides of the following composition, percent by weight:

    ______________________________________                                                 Dy.sub.2 O.sub.3                                                                     67.772                                                                   Al.sub.2 O.sub.3                                                                     30.877                                                                   ZrO.sub.2                                                                            1.35                                                             ______________________________________                                    

The thus-produced crystal is not transparent and has a dark-cherry shade. In small-size articles the material has the colour close to that of almandines and pyropes.

EXAMPLE 4

A single-crystalline material based on dysprosium-aluminium garnet Dy₃ Al₅ O₁₂ containing zirconium as the dyeing additive in the amount of 0.56% by weight is obtained in a manner similar to that described in Example 1. As the starting components a mixture of oxides of the following composition is used, percent by weight:

    ______________________________________                                                 Dy.sub.2 O.sub.3                                                                     68.184                                                                   Al.sub.2 O.sub.3                                                                     31.065                                                                   ZrO.sub.2                                                                            0.75                                                             ______________________________________                                    

The thus-produced crystal has an intensive cherry-red colour.

EXAMPLE 5

A single-crystalline material based on lutecium-aluminium garnet Lu₃ Al₅ O₁₂ containing zirconium as the dyeing additive in the amount of 0.53% by weight is prepared in a manner similar to that described in Example 1 hereinbefore. As the starting components a mixture of the following composition is used, percent by weight:

    ______________________________________                                                 Lu.sub.2 O.sub.3                                                                     69.22                                                                    Al.sub.2 O.sub.3                                                                     30.06                                                                    ZrO.sub.2                                                                             0.72                                                            ______________________________________                                    

The thus-produced crystal has an intensive red colour.

EXAMPLE 6

A single-crystalline material based on holmium-aluminium garnet Ho₃ Al₅ O₁₂ containing zirconium as the dyeing additive in the amount of 0.4% by weight is produced in a manner similar to that of Example 1. As the starting components a mixture of the following oxides is used, percent by weight:

    ______________________________________                                                 Ho.sub.2 O.sub.3                                                                     68.63                                                                    Al.sub.2 O.sub.3                                                                     30.87                                                                    ZrO.sub.2                                                                            0.5                                                              ______________________________________                                    

The thus-produced crystal has a red-yellow-brown colour.

EXAMPLE 7

A single-crystalline material based on erbium-aluminium garnet Er₃ Al₅ O₁₂ containing zirconium as the dyeing additive in the amount of 0.4% by weight is produced in a manner similar to that described in Example 1. As the starting components a mixture of the following oxides is used, percent by weight:

    ______________________________________                                                 Er.sub.2 O.sub.3                                                                     68.88                                                                    Al.sub.2 O.sub.3                                                                     30.62                                                                    ZrO.sub.2                                                                            0.5                                                              ______________________________________                                    

The thus-produced crystal has a reddish-brown colour.

The single-crystalline material according to the present invention based on aluminium garnets can be useful, in particular, in the manufacture of insertion pieces for jewelry.

Incorporation of zirconium into yttrium-aluminium garnet imparts to the latter a red colour of different shades close to those of naturally-occurring almandines and pyropes. 

We claim:
 1. A single-crystalline aluminum garnet material consisting of Re₃ Al₅ O₁₂ and 10⁻² to 3% by weight of the dyeing additive zirconium, wherein Re is an element from the group consisting of yttrium, dysprosium, holmium, erbium, and lutecium.
 2. A single-crystalline material according to claim 1, wherein Re is yttrium and said material imparts a red color.
 3. A single crystalline material according to claim 1, wherein Re is dysprosium and said material imparts a cherry color.
 4. A single-crystalline material according to claim 1, wherein Re is holmium and said material imparts a reddish brown color.
 5. A single-crystalline material according to claim 1, wherein Re is erbium and said material imparts a red-yellow-brown color.
 6. A single-crystalline material according to claim 1, wherein Re is lutecium and said material imparts a red color. 